Fix handling of PIN deletion with enabled biometrics

[myxmaster]

Describe the bug

For a good reason, biometrics can only be enabled if a PIN or password is set. But currently you can work around this by deleting the PIN or password after biometrics have been enabled. This leads to not having any fallback in case the finger/face or sensor is lost or damaged (lol).

Instead we should disable biometrics in this case when deleting a PIN or password (and show a warning about this).

Reproduce

Zeus version

v0.8.0

Node interface

LND (REST)

Network

Clearnet

Device

Samsung Galaxy S20+

Device operating system

Android 13

Log output

No response